Engine hours when buying a used trawler

[Valone123]

Almost all listings include engines hours, but I don’t have a good reference point. How many hours are “too many” when looking at a trawler? At what point can you expect a major engine overhaul or replacement? Thanks.

 

[psneeld]

You have asked an impossible question.

Make, model, maintenance and operation matter as a minimum.

You will get lots of answers with tidbits of the truth.....some with some only opinion to be wary of....

After hundreds af posts and outside research...then ge confident of your own opinion.

 

[firehoser75]

Scott has it right.
I know another Nordic Tug 37 owner who has over 10,000 hours on his well maintained Cummins engine. However, the engine has been run at hull speed (or less) for it's whole life (basically 1/2 throttle) and been carefully maintained and used regularly.

Then there is the other extreme. A boat that is hardly ever used, or has sat for long periods of time unused and/or uncared for. Even with low hours, this is often not a good thing for the engine.

Another factor is how was the engine used. Lightly used, usually not hard on the engine. Run near the top (run hard) and/or (worse) overloaded, is not a good thing for long engine life.

So many factors involved, but finding an engine that has been used regularly, carefully and properly maintained, and operated "lightly", is probably a good combination.
Finding out the correct and true information about an engine can be difficult.

 

[psneeld]

Or what many here are afraid of....know the cost of an engine replacement and buy the trawler for that cost less plus aggravation cost. Many may live with that over asking price.

I might do the same in a few years when I go to sell.

 

[ghost]

Hours are meaningless for all but a few obvious examples. They are there because nothing else accurately measure engine condition, but that does not make them useful, just the only thing readily publishable. So people like to imagine useful rules for them. Mostly hogwash based on an over abundance of cognitive bias (basically humans take one example and over extrapolate to other situations not backed by real data).

Beware very low hours (engines don’t like to sit) and extraordinarily high hours (like over 30k). Except maybe over 30k hours already had an expensive rebuild and is exactly the engines you want to buy. So scratch the high hours, beware super low hours. Anything else, you need demonstrated ability to run and a thorough maintenance history to take a guess. Expect you won’t get a sufficient history in most cases, so don’t form an opinion on a few receipts here and there.

Sorry, hard truth.

Get a dedicated engine survey. Yeah, it will cost you, but worth it. The availability of LOCAL mechanics for that engine package is probably a better indicator of your happiness as much as the engines themselves.

 

[DavidM]

As others have noted above, marine diesel hours are meaningless for recreational boats. Engines get trashed for several reasons:

Marine components fail due to lack of maintenance. This is the most common. A high output turbocharged engine's after cooler can fail in less than a thousand hours (but probably ten years or so time to failure). When it fails it can trash the engine due to salt water getting through to the air side. This is one example. Main heat exchangers, water injection elbows, etc, all can fail and ruin an engine.

The core engine wears out due to overloading. Most high output marine engines need to be run at no more than 80% of max rpm or about 50% power loading otherwise rings can wear, valves can fail, etc.

The core engine wears out due to normal use at reasonable loadings. This will take ten thousand hours or better and recreational engines rarely see that much use.

Most of these potential problems can be found with a good engine survey, not by looking at the hour meter.

David

 

[Nick14]

FWIW, I've had a few diesel engineers tell me that total fuel consumption is a more accurate measurement of the life of an engine. This makes sense; an engine that's been run lightly (not WOT all the time) will have consumed less fuel. On the other hand, an engine that's been run hard at or near WOT will have consumed a lot of fuel.

It comes down to physics. More fuel consumed = more thermal and physical stresses have been placed on the engine, both moving and stationary parts.

In conversations with diesel engineers over the years, I've had a few mention to me the rated service lives in terms of total fuel consumed of various mid-sized pleasure boat engines (in the 5-8 liter displacement range), which have ranged from 30,000-50,000 gallons. How that might translate into hours again depends on how it's been run. An engine with a nominal 35,000 gallon service life, used gently at say around 3 GPH could theoretically = >10,000 hours. On the other hand, the same engine run at 80% of WOT most of the time and 15 GPH might last 2,500 hours.

Some people have the what I believe is misconception that 'diesel engines last forever'. I think that perception may have been formed from the old-school diesels, like the venerable Detroit 6-71 in its original, naturally aspirated form. That was a 426 cu in 2,200 lb beast that put out all of 165 hp. Yes, it was primitive, but also over-built and massively under-stressed. I've heard stories of those engines lasting 20,000+ hours.

Many modern diesel engines are different animals. They are much lighter, more "efficient", but also more highly stressed. Many are turbocharged to within an inch of their lives, which increases power output, as well as fuel consumption, and correspondingly shortens service life. Consider the Yanmar 6LPA, 256 cu in, 899 lbs, yet produces 315 hp, or the 6LY at 354 cu in and up to 480 hp and only 1,179 lbs - half the weight of the 6-71 yet three times the power output. An engine like that is certainly more efficient, but won't last as long.

The almost as venerable CAT3208, 636 cu in, might be putting out 210 hp, or 435 hp. The latter will use more fuel and generally have a shorter life than the former.

Throw in the major variables of how an engine has been maintained, how it's been operated, and the answer is, it depends, and varies widely.

The late David Pascoe, marine surveyor (yes, I know, his name can be controversial and some people disagree with his views, but I've found that's sometimes because he's saying things they don't want to hear) has written on the topic. Some of his writings are still up on the yachtsurvey website:

https://www.yachtsurvey.com/engines.htm

 

[psneeld]

Gallons, hours, owners, boat types, operations.....it's all a gamble.....ya never know for sure.

Sure records, etc....... MAY have something to factor in...but you still never know.

If you aren't ready to replace/rebuild/repair engines one minute after you sign the agreement.... good luck.

I ran a brand new boat one day with 3 hrs on the engines and one blew a turbo and luckily I shut it down before pieces got sucked in through any valves. Still a big deal and fortunately under warranty.

Goes to show.....anytime....any place.

 

[Comodave]

Years ago I was talking to Bob Smith of American Diesel. He said the watermen on the Chesapeake brought their Lehmans in for routine PM rebuilds at 20,000 hours. But those engines were run regularly and well maintained. Recreational engines sit much more and as a result generally don’t last as long. But 5 to 10 thousand hours isn’t unreasonable if the engine is maintained.

 

[Nick14]

Gallons, hours, owners, boat types, operations.....it's all a gamble.....ya never know for sure.

Sure records, etc....... MAY have something to factor in...but you still never know.

If you aren't ready to replace/rebuild/repair engines one minute after you sign the agreement.... good luck.

I ran a brand new boat one day with 3 hrs on the engines and one blew a turbo and luckily I shut it down before pieces got sucked in through any valves. Still a big deal and fortunately under warranty.

Goes to show.....anytime....any place.

LOL! That's the best and most realistic advice!

Last year I looked at a boat for sale. One of the appeals of it was the low hours, 600 (for a 2001 model year). A few months later it reappeared on the market, with new (rebuilt) engines installed! I talked with the owner who told me that one of the original engines 'just blew' (threw a rod through the block). After only 600 hours.

 

[psneeld]

Years ago I was talking to Bob Smith of American Diesel. He said the watermen on the Chesapeake brought their Lehmans in for routine PM rebuilds at 20,000 hours. But those engines were run regularly and well maintained. Recreational engines sit much more and as a result generally don’t last as long. But 5 to 10 thousand hours isn’t unreasonable if the engine is maintained.

All it takes is an inattentive couple of minutes by a conscientious, experienced owner to cook an engine from a plastic bag or other to turn a 10,000/20,000 hr engine into a pile of junk at 1000. Or a factory defect at the same.

 

[backinblue]

Scott has it right.
I know another Nordic Tug 37 owner who has over 10,000 hours on his well maintained Cummins engine. However, the engine has been run at hull speed (or less) for it's whole life (basically 1/2 throttle) and been carefully maintained and used regularly.

Then there is the other extreme. A boat that is hardly ever used, or has sat for long periods of time unused and/or uncared for. Even with low hours, this is often not a good thing for the engine.

Another factor is how was the engine used. Lightly used, usually not hard on the engine. Run near the top (run hard) and/or (worse) overloaded, is not a good thing for long engine life.

So many factors involved, but finding an engine that has been used regularly, carefully and properly maintained, and operated "lightly", is probably a good combination.
Finding out the correct and true information about an engine can be difficult.

I thought it was better for a diesel to be run at a higher load rather than "lightly". My Yanmar manual says it should run at 80% of max RPM for 90% of the time (or something close to that). Does it depend on the make and/or age of the engine?

 

[backinblue]

I do agree that unusually low hours is a bad sign. I would say the same for autos and motorcycles.

 

[Jeff F]

I thought it was better for a diesel to be run at a higher load rather than "lightly". My Yanmar manual says it should run at 80% of max RPM for 90% of the time (or something close to that). Does it depend on the make and/or age of the engine?

I don't think that's what your manual says. Sorry to be disagreeable.

 

[backinblue]

I don't think that's what your manual says. Sorry to be disagreeable.

It does say that it is designed to run safely at 80% of max RPM for 90% of runtime. I stand corrected in that it does not say that this is recommended over running at a lower RPM. However, I do believe it is not healthy to run a diesel at fairly low RPMs for extended periods of time.

 

[psneeld]

One has to compare engine duty cycle rating or it thin air discussion.

 

[backinblue]

One has to compare engine duty cycle rating or it thin air discussion.

Up until a couple years ago, I owned only sailboats so I'm willing to listen and learn. If my boat is able to plane and is most efficient (mpg) at 80% of WOT, isn't that where I would normally want to operate most of the time unless I am at or below displacement speed?

 

[rslifkin]

It does say that it is designed to run safely at 80% of max RPM for 90% of runtime. I stand corrected in that it does not say that this is recommended over running at a lower RPM. However, I do believe it is not healthy to run a diesel at fairly low RPMs for extended periods of time.

Running at light load is engine dependent. Some engines don't get various components hot enough or have poor combustion under light load and don't do well running gently for long periods of time. Others don't seem to care.

My own gas 454s suffer from one issue under light load: low oil temperatures. As I type this they're humming along quite happily at just over 1300 rpm. But the oil temps are only about 160 right now. So for the last few minutes of this run I'll jump up on plane to get the oil for and hot so I can burn off any fuel or moisture that isn't evaporating well enough at this temperature.

 

[gsholz]

I have been looking at some boats with allegedly "bulletproof" big and heavy diesel engines such as the CAT 3406 or 3408 with only 1000 to 1500 hours in 20 years.

I'm surprised to find many had major engine work or have already been completely overhauled at those low hours. These engines will run 10-20,000 hours in (derated) commercial use but barely make it to 2000 in pleasure use. Recreational use and lack of maintenance is killing these engines pre-maturely. Seawater cooled aftercoolers seem to have a high failure rate as owners hesitate to spend the big dollars to have them maintained every 2 years or replaced every 6 years as CAT requires.

Now, the naturally aspirated 3208NAs in my last boat did make it to 7,300 hours (and probably many more) but they were dinosaurs. 10+ liter of displacement, only 210hp, no turbo, no aftercooler, no electronics. Very little to go wrong. A Cummins 6BT (210 hp) would be closest modern engine today for displacement trawler use.

 

[psneeld]

Up until a couple years ago, I owned only sailboats so I'm willing to listen and learn. If my boat is able to plane and is most efficient (mpg) at 80% of WOT, isn't that where I would normally want to operate most of the time unless I am at or below displacement speed?

You have to know the duty rating cycle of you engine to know what load ranges are recommended and for how long you should operate in them. So no one cant answer you question without knowing those/ looking them up/ having the same engine.

Plus some claim Lehmans should run at 80% too, while others have heard that a much, much lower load rating makes them last longer ( after all they failed their primary assignment and are something like a 60 year old design).

 

[Jeff F]

Up until a couple years ago, I owned only sailboats so I'm willing to listen and learn. If my boat is able to plane and is most efficient (mpg) at 80% of WOT, isn't that where I would normally want to operate most of the time unless I am at or below displacement speed?

Yes. And in some cases that may be perfectly fine. But 80% load 90% of the time is a heavy duty rating not found in most recreational diesels in planing boats. I'd associate that use with larger lower hp motors.

Most of us like to learn. What motors and hp rating do you have? I'm curious about Yanmar, having studied Cummins and John Deere ratings quite carefully.

 

[Moonfish]

I always say one should apply the Goldilocks engine hour rule: Too many hours or too few hours and it just doesn't taste quite right...

 

[backinblue]

Yes. And in some cases that may be perfectly fine. But 80% load 90% of the time is a heavy duty rating not found in most recreational diesels in planing boats. I'd associate that use with larger lower hp motors.

Most of us like to learn. What motors and hp rating do you have? I'm curious about Yanmar, having studied Cummins and John Deere ratings quite carefully.

315 HP Yanmar 6lpa-stp2. Built in 2011. I just sent Yanmar an email. I have found them to be pretty responsive. Their Op manual is vague saying that it should be run at 80% of max RPM or less, for 90% of the time. It doesn't say whether less is better or how much less or what should be considered optimal or desired RPM for extended cruises.

 

[firehoser75]

I thought it was better for a diesel to be run at a higher load rather than "lightly". My Yanmar manual says it should run at 80% of max RPM for 90% of the time (or something close to that). Does it depend on the make and/or age of the engine?

Nick has explained it well in the following:
"FWIW, I've had a few diesel engineers tell me that total fuel consumption is a more accurate measurement of the life of an engine. This makes sense; an engine that's been run lightly (not WOT all the time) will have consumed less fuel. On the other hand, an engine that's been run hard at or near WOT will have consumed a lot of fuel.

It comes down to physics. More fuel consumed = more thermal and physical stresses have been placed on the engine, both moving and stationary parts."
According to Tony Athens, and others, it is not good to run a diesel at idle or especially no load (like warm ups at the dock) for any extended period of time. Start up the engine, and cast off reasonably quickly so that the engine warms up under load at RPM's below 1000 or so. However, it does not "hurt" a diesel to run under load at lower rpms compared to the 80% figure you are mentioning. The only real issue is ensuring that the engine reaches operating temperatures (does not run too cool (or too hot)), and especially if turbo charged, that it is run up to the 80% rpm or even WOT for 10 minutes or so every so often to "burn out' any carbon that might buildup. That is how the NT owner I discussed who goes from Seattle to Alaska every year and now has over 10,000 hours on his Cummins 6BTA operates his boat. He cruises almost all the time at 13-1400 RPM (engine is rated at 2800 WOT) and his engine operates at 180-185 degrees at that RPM.

Tony states the same about "total fuel consumption" being one, very important indicator of "expected" engine life (all things being equal).
For those who don't know, Tony Athens is known as a marine diesel guru with over 35 years experience. His very informative website is: sbmar.com. I have no affiliation with him other than he has taught me a lot (for free) and I have purchased a few parts from him over the years. But yes, if you want to run a boat on plane all or most of the time, in most cases that will mean you will run your engine at approx. 80% throttle most of the time. Just be aware, that using the principle of fuel consumed, it will probably "wear out" (main internal engine parts) faster than the same engine run at hull speed at half throttle, all other things being equal. Remember all of this is "in theory" and real world results may differ.

 

[psneeld]

Using fuel is great yardstick on test cell engines, it is a guide for one engine and its life but there is more to the story if trying to compare engines or figure out the condition of a particular engine.

Sure if the engine was fed a perfect life since purchase, you might know hiow far along to normal rebuild time. Most recreational engines are so far below that number its funny to worry about being worn out....except for some models.

The million dollar question is, did the previous owner do anything or not do something that has caused major damage.

Thus oil sampling records, an honest logbook, etc....

And its still only a guess.

 

[backinblue]

Even if total fuel consumption is a great predictor of engine life, it's pretty irrelevant because where have you ever found a boat with an accurate record of fuel consumption since new? It makes great sense in theory, but why does it matter if it's data you don't have?

Mileage on a car is similar to marine engine hours. It's only 1 data point and does tell you something, but is not very meaningful on its own.

 

[psneeld]

Many larger vessels keep logs with fuel consumed.

I do.

But I agree, its only one metric on engine condition.

 

[firehoser75]

I think the main points are valid. Ongoing regular OEM approved maintenance, how the engine was operated (run hard, overloaded, or run relatively easily and here is where the concept of fuel consumption comes in (at least partially)), the concept of "marine age" (or the ongoing ravages of living in a saltwater environment) are probably more meaningful than "counted engine hours".

Engine hours are usually easily determined, the other items, not so much.
I agree totally, actual engine condition is a "complex subject".

 

[psneeld]

Newer engines may have all serious events logged that can be accessed by dealer techs...which an engine survey may reveal..older engines need owner honesty.

 

[Jeff F]

315 HP Yanmar 6lpa-stp2. Built in 2011. I just sent Yanmar an email. I have found them to be pretty responsive. Their Op manual is vague saying that it should be run at 80% of max RPM or less, for 90% of the time. It doesn't say whether less is better or how much less or what should be considered optimal or desired RPM for extended cruises.

Thanks. I did some online sleuthing, and the only prohibition I saw was on continuous full power operation. Continuous operation at 50-100 rpm less than rated hp is specifically allowed without restriction, assuming propped correctly. That's something like 90% of available power.

Sorry for hijacking the conversation. I learned something!